Devices for dispersing a liquid such as, for example, air freshening device in which there is a slow release of vapor into air from a liquid are well known in the art. However, such devices typically rely on passive evaporation of the liquid from a wick. Most commonly, one end of a wick is placed in a fluid to be dispersed, while the other end is exposed to the atmosphere. Capillary action forces liquid through the wick and up to the exposed end, where the liquid evaporates from the end of the wick and into the surrounding atmosphere. These devices are generally known to have the disadvantages of dispersing the liquid at an uneven rate and composition. For example, the more volatile components of the liquid mixture will evaporate faster thereby leaving an increasingly greater percentage of the less-volatile components in the remaining composition.
Devices for spraying liquid into the surrounding atmosphere using electrostatic force are also well known in the art. In these devices, the liquid is typically delivered to the point of high electric potential through, for example, capillary rise in a small diameter tube. The liquid is drawn out by electrostatic forces into ligaments which break up into fine droplets. While these devices can be effective under certain circumstances, such as when the transfer of liquid greatly exceeds the evaporation rate, they typically require relatively high voltage to operate properly and can be somewhat fragile.
Still other devices are known which employ gravitational forces to diffuse liquid through a membrane. One side of a membrane is exposed to liquid and the other side is exposed to the atmosphere. The liquid diffuses through the membrane and volatilizes into the surrounding atmosphere from the exposed surface of the membrane at a rate dependent on the porosity of the membrane.
While the foregoing controlled delivery systems sufficiently disperse liquids for some applications, they fail to provide a controlled, steady release of liquid over an extended period of time. More specifically, they do not disperse the active ingredient consistently over time. They also fail to adequately disperse non-volatile liquids, liquids of higher viscosity and gels.
There is a need, therefore, for a device for consistently dispersing liquid over time, that is easy to use and inexpensive to manufacture.